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Shallow granular avalanches on slopes close to repose exhibit hysteretic behaviour. For instance, when a steady-uniform granular flow is brought to rest it leaves a deposit of thickness
on a rough slope inclined at an angle
to the horizontal. However, this layer will not spontaneously start to flow again until it is inclined to a higher angle
, or the thickness is increased to
. This simple phenomenology leads to a rich variety of flows with co-existing regions of solid-like and fluid-like granular behaviour that evolve in space and time. In particular, frictional hysteresis is directly responsible for the spontaneous formation of self-channelized flows with static levees, retrogressive failures as well as erosion–deposition waves that travel through the material. This paper is motivated by the experimental observation that a travelling-wave develops, when a steady uniform flow of carborundum particles on a bed of larger glass beads, runs out to leave a deposit that is approximately equal to
. Numerical simulations using the friction law originally proposed by Edwards et al. (J. Fluid Mech., vol. 823, 2017, pp. 278–315) and modified here, demonstrate that there are in fact two travelling waves. One that marks the trailing edge of the steady-uniform flow and another that rapidly deposits the particles, directly connecting the point of minimum dynamic friction (at thickness
) with the deposited layer. The first wave moves slightly faster than the second wave, and so there is a slowly expanding region between them in which the flow thins and the particles slow down. An exact inviscid solution for the second travelling wave is derived and it is shown that for a steady-uniform flow of thickness
it produces a deposit close to
for all inclination angles. Numerical simulations show that the two-wave structure deposits layers that are approximately equal to
for all initial thicknesses. This insensitivity to the initial conditions implies that
is a universal quantity, at least for carborundum particles on a bed of larger glass beads. Numerical simulations are therefore able to capture the complete experimental staircase procedure, which is commonly used to determine the
curves by progressively increasing the inclination of the chute. In general, however, the deposit thickness may depend on the depth of the flowing layer that generated it, so the most robust way to determine
is to measure the deposit thickness from a flow that was moving at the minimum steady-uniform velocity. Finally, some of the pathologies in earlier non-monotonic friction laws are discussed and it is explicitly shown that with these models either steadily travelling deposition waves do not form or they do not leave the correct deposit depth
Principia Logico-Metaphysica contains a foundational logical theory for metaphysics, mathematics, and the sciences. It includes a canonical development of Abstract Object Theory [AOT], a metaphysical theory (inspired by ideas of Ernst Mally, formalized by Zalta) that distinguishes between ordinary and abstract objects.
This article reports on recent work in which AOT has been successfully represented and partly automated in the proof assistant system Isabelle/HOL. Initial experiments within this framework reveal a crucial but overlooked fact: a deeply-rooted and known paradox is reintroduced in AOT when the logic of complex terms is simply adjoined to AOT’s specially formulated comprehension principle for relations. This result constitutes a new and important paradox, given how much expressive and analytic power is contributed by having the two kinds of complex terms in the system. Its discovery is the highlight of our joint project and provides strong evidence for a new kind of scientific practice in philosophy, namely, computational metaphysics.
Our results were made technically possible by a suitable adaptation of Benzmüller’s metalogical approach to universal reasoning by semantically embedding theories in classical higher-order logic. This approach enables one to reuse state-of-the-art higher-order proof assistants, such as Isabelle/HOL, for mechanizing and experimentally exploring challenging logics and theories such as AOT. Our results also provide a fresh perspective on the question of whether relational type theory or functional type theory better serves as a foundation for logic and metaphysics.
A national need is to prepare for and respond to accidental or intentional disasters categorized as chemical, biological, radiological, nuclear, or explosive (CBRNE). These incidents require specific subject-matter expertise, yet have commonalities. We identify 7 core elements comprising CBRNE science that require integration for effective preparedness planning and public health and medical response and recovery. These core elements are (1) basic and clinical sciences, (2) modeling and systems management, (3) planning, (4) response and incident management, (5) recovery and resilience, (6) lessons learned, and (7) continuous improvement. A key feature is the ability of relevant subject matter experts to integrate information into response operations. We propose the CBRNE medical operations science support expert as a professional who (1) understands that CBRNE incidents require an integrated systems approach, (2) understands the key functions and contributions of CBRNE science practitioners, (3) helps direct strategic and tactical CBRNE planning and responses through first-hand experience, and (4) provides advice to senior decision-makers managing response activities. Recognition of both CBRNE science as a distinct competency and the establishment of the CBRNE medical operations science support expert informs the public of the enormous progress made, broadcasts opportunities for new talent, and enhances the sophistication and analytic expertise of senior managers planning for and responding to CBRNE incidents.
When a layer of static grains on a sufficiently steep slope is disturbed, an upslope-propagating erosion wave, or retrogressive failure, may form that separates the initially static material from a downslope region of flowing grains. This paper shows that a relatively simple depth-averaged avalanche model with frictional hysteresis is sufficient to capture a planar retrogressive failure that is independent of the cross-slope coordinate. The hysteresis is modelled with a non-monotonic effective basal friction law that has static, intermediate (velocity decreasing) and dynamic (velocity increasing) regimes. Both experiments and time-dependent numerical simulations show that steadily travelling retrogressive waves rapidly form in this system and a travelling wave ansatz is therefore used to derive a one-dimensional depth-averaged exact solution. The speed of the wave is determined by a critical point in the ordinary differential equation for the thickness. The critical point lies in the intermediate frictional regime, at the point where the friction exactly balances the downslope component of gravity. The retrogressive wave is therefore a sensitive test of the functional form of the friction law in this regime, where steady uniform flows are unstable and so cannot be used to determine the friction law directly. Upper and lower bounds for the existence of retrogressive waves in terms of the initial layer depth and the slope inclination are found and shown to be in good agreement with the experimentally determined phase diagram. For the friction law proposed by Edwards et al. (J. Fluid. Mech., vol. 823, 2017, pp. 278–315, J. Fluid. Mech., 2019, (submitted)) the magnitude of the wave speed is slightly under-predicted, but, for a given initial layer thickness, the exact solution accurately predicts an increase in the wave speed with higher inclinations. The model also captures the finite wave speed at the onset of retrogressive failure observed in experiments.
X-ray diffraction topographs obtained in the anomalous transmission geometry contain images which are quite different from those obtained from thin crystals (μL<=l). In this paper various topographic images which are unique to thick crystals (μL>10) will be presented and discussed in terms of dynamical diffraction in imperfect crystals. First, it is observed in topographs that images of crystal imperfections caused by disruption of the anomalous transmission effect are slightly broader or more diffuse in the H-diffracted (Bragg-diffracted) beam than in the O-diffracted (transmitted beam). These observations have been made in both copper and nickel crystals. Such broadening can be explained by the presence of unique extinction terms in the expression for the intensity of the dynamically diffracted beam in an imperfect crystal.
The Middle Nile (from Aswan in Egypt to Khartoum in Sudan, Fig. 6.1) is quite exceptional in Sub-Saharan Africa. It is a region where, from the beginning, archaeological frameworks have been constructed largely on the basis of cemetery excavations. This has, of course, much to do with regionally specific research histories and emergent archaeological practices associated with them. The traditions of materially rich mortuary cultures encountered in the Middle Nile, dating back to the early Neolithic period (here the sixth millennium BC), has continued to attract significant archaeological attention. Numerous, often large, cemeteries are still routinely being explored within the context of both research and rescue archaeology. Their material abundance continues to fascinate. The first extensive archaeological survey of Nubia, completed in 1911, excavated more than 8,200 graves in 151 cemeteries within a ‘survey’ area limited to the riverine oasis and covering an area of less than 250 km2.
There is community concern about the treatment of farm animals post-farm gate, particularly animal transport and slaughter. Relationships between lamb behavioural and physiological variables on farm, stockperson, dog and lamb behavioural variables pre-slaughter and plasma cortisol, glucose and lactate in lambs post-slaughter were studied in 400 lambs. The lambs were observed in three behavioural tests, novel arena, flight distance to a human and temperament tests, before transport for slaughter. Closed-circuit television video footage was used to record stockperson, dog and lamb behaviour immediately before slaughter. Blood samples for cortisol, glucose and lactate analyses were collected on farm following the three behavioural tests and immediately post-slaughter. The regression models that best predicted plasma cortisol, glucose and lactate concentrations post-slaughter included a mixture of stockperson and dog behavioural variables as well as lamb variables both on-farm and pre-slaughter. These regression models accounted for 33%, 34% and 44% of the variance in plasma cortisol, glucose and lactate concentrations post-slaughter, respectively. Some of the stockperson and dog behaviours pre-slaughter that were predictive of the stress and metabolic variables post-slaughter included the duration of negative stockperson behaviours such as fast locomotion and lifting/pulling lambs, and the duration of dog behaviours such as lunging and barking at the lamb, while some of the predictive lamb behaviour variables included the durations of jumping and fleeing. Some of the physiological and behavioural responses to the behavioural tests on farm were also predictive of the stress and metabolic variables post-slaughter. These relationships support the well-demonstrated effect of handling on fear and stress responses in livestock, and although not direct evidence of causal relationships, highlight the potential benefits of training stockpeople to reduce fear and stress in sheep at abattoirs.
Objectives: Caregivers of youth with heavy prenatal alcohol exposure report impaired communication, which can significantly impact quality of life. Using data collected as part of the Collaborative Initiative on Fetal Alcohol Spectrum Disorders (CIFASD), we examined whether cognitive variables predict communication ability of youth with histories of heavy prenatal alcohol exposure. Methods: Subjects (ages 10–16 years) comprised two groups: adolescents with heavy prenatal alcohol exposure (AE) and non-exposed controls (CON). Selected measures of executive function (NEPSY, Delis-Kaplan Executive Function System), working memory (CANTAB), and language were tested in the child, while parents completed communication ratings (Vineland Adaptive Behavior Scales – Second Edition). Separate multiple regression analyses determined which cognitive domains predicted communication ability. A final, global model of communication comprised the three cognitive models. Results: Spatial Working Memory and Inhibition significantly contributed to communication ability across groups. Twenty Questions performance related to communication ability in the CON group only while Word Generation performance related to communication ability in the AE group only. Effects remained significant in the global model, with the exception of Spatial Working Memory. Conclusions: Both groups displayed a relation between communication and Spatial Working Memory and Inhibition. Stronger communication ability related to stronger verbal fluency in the AE group and Twenty Questions performance in the CON group. These findings suggest that alcohol-exposed adolescents may rely more heavily on learned verbal storage or fluency for daily communication while non-exposed adolescents may rely more heavily on abstract thinking and verbal efficiency. Interventions aimed at aspects of executive function may be most effective at improving communication ability of these individuals. (JINS, 2018, 24, 1026–1037)
Reconstruction of lake-level fluctuations from landform and outcrop evidence typically involves characterizing periods with relative high stands. We developed a new approach to provide water-level estimates in the absence of shoreline evidence for Owens Lake in eastern California by integrating landform, outcrop, and existing lake-core data with wind-wave and sediment entrainment modeling of lake-core sedimentology. We also refined the late Holocene lake-level history of Owens Lake by dating four previously undated shoreline features above the water level (1096.4 m) in AD 1872. The new ages coincide with wetter and cooler climate during the Neopluvial (~3.6 ka), Medieval Pluvial (~0.8 ka), and Little Ice Age (~0.35 ka). Dates from stumps below 1096 m also indicate two periods of low stands at ~0.89 and 0.67 ka during the Medieval Climatic Anomaly. The timing of modeled water levels associated with 22 mud and sand units in lake cores agree well with shoreline records of Owens Lake and nearby Mono Lake, as well as with proxy evidence for relatively wet and dry periods from tree-ring and glacial records within the watershed. Our integrated analysis provides a continuous 4000-yr lake-level record showing the timing, duration, and magnitude of hydroclimate variability along the south-central Sierra Nevada.
Piglet survival is based on a complex interaction between the piglets own genetic component (direct genetic effects), the dams genetic contribution (maternal genetic effects) and environmental effects (systematic environmental such as year-season, common litter and individual environmental effects). Disentanglement of direct and maternal genetic effects needs a powerful design of genetic relationships. In order to accomplish this, a two generation selection experiment was designed with different selection groups for direct and maternal effects and cross-classification of these selection groups. Survival at birth and survival during the nursing period may have genetically independent components and would then be treated as different traits. In addition, piglet survival traits are reported to have low direct and maternal heritabilities and traits genetically associated with survival, such as birth weight, may result in a more efficient change in survival than using survival per se. Therefore, the objective of the research was to estimate the genetic parameters of direct and maternal genetic effects of survival and birth weight in order to enhance the selection strategies for piglet survival.
Recently much research has been carried out to enhance piglet survival by genetic improvement. Heritabilities of traits associated with piglet survival are generally low, but the genetic variation is large enough to provide improvement through breeding (Knol et al., 2002). However, correlations between some traits and/or between maternal and direct genetic effects have shown contradictory results, and not many studies have considered these effects. Reports of correlations between piglet survival traits and production traits are even fewer. The aim of this study was to estimate heritabilities of piglet survival traits and their genetic associations with other reproduction traits as well as production traits, using a Bayesian approach and appropriate models and genetic statistical procedures in order to obtain more accurate genetic parameters.
Lactic acid bacteria (LAB) consist of many genera, which contain numerous bacterial species. The LAB are Gram-positive, non-spore forming micro-organisms and typically give negative results to the catalase test (Stiles and Holzapfel, 1997). The current classification of LAB combines both phenotypic properties and genotypic examination. Phenotypic studies use the cell wall compositions (mainly for Bifidobacteria), protein fingerprinting which analyse the total soluble cytoplasmic proteins, and the patterns of certain isoenzymes. The gold-standard molecular method to identify LAB is DNA-DNA homology analysis, and molecular methods using specific genetic material patterns of LAB are increasingly being applied as an identification tool. The objective of this study was to develop potential specific oligonucleotide probes for the macro-array identification of LAB.
Recent research suggests that the genetic makeup of a pig may contribute to the expression of tail biting (Breuer et al., 2002). To date there has been little investigation into the genetics of tail biting. A significant population of tail biters was found at a commercial pig breeding farm at which an experiment on the genetic basis of the expression of harmful social behaviour was being performed. As pedigree data for each pig on the farm were available, the opportunity was taken to investigate the heritability of tail biting by recording the perpetrators of clinical tail biting.
The Taipan galaxy survey (hereafter simply ‘Taipan’) is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, |b| ≳ 10°), and obtain optical spectra for about two million galaxies out to z < 0.4. Taipan will use the newly refurbished 1.2-m UK Schmidt Telescope at Siding Spring Observatory with the new TAIPAN instrument, which includes an innovative ‘Starbugs’ positioning system capable of rapidly and simultaneously deploying up to 150 spectroscopic fibres (and up to 300 with a proposed upgrade) over the 6° diameter focal plane, and a purpose-built spectrograph operating in the range from 370 to 870 nm with resolving power R ≳ 2000. The main scientific goals of Taipan are (i) to measure the distance scale of the Universe (primarily governed by the local expansion rate, H0) to 1% precision, and the growth rate of structure to 5%; (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics; and (iii) to deliver a legacy sample of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited sample (i ⩽ 17) of about 1.2 × 106 galaxies supplemented by an extension to higher redshifts and fainter magnitudes (i ⩽ 18.1) of a luminous red galaxy sample of about 0.8 × 106 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated ‘virtual observer’ software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio; it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.
Two observational programs which provide new information about particular LBVs through investigations of their immediate surroundings are described. (1) Digital spectral classification of OB supergiants in compact groups apparently associated with Radcliffe 127 and S Doradus has revealed several interesting objects and indicates which of them are likely to be generically related to the LBVs. (2) Velocity-resolved images of the Eta Carinae shell show qualitatively new features, which will contribute substantially to the interpretation of its complex spatial/kinematical structure.
An antenna in geostationary orbit was used for VLBI observations at 2.3 GHz, in combination with ground antennas in Australia and Japan. 23 of the 25 observed sources were detected on orbiter-ground baselines, with baseline lengths as large as 2.15 earth diameters. Brightness temperatures between 1012 K and 4 × 1012 K were measured for 10 sources.